Abstract Obesity increases risks of developing several chronic metabolic disorders, including diabetes, cardiovascular disease, and some forms of cancer. Brown adipose tissue (BAT), a fat tissue type responsible for non- shivering thermogenesis and now known to exist in adult humans, has emerged as a novel target to increase energy expenditure, reduce white fat accumulation and inflammation, and improve systemic metabolism. The goal of this proposal is to explore the role of epoxide signaling lipids (mainly EETs derived from n-6 arachidonic acid and EDPs from n-3 docosahexaenoic acid) and inhibition of soluble epoxide hydrolase (sEH), the enzyme that hydrolyzes these epoxides into less active diols, on brown adipogenesis in vitro and in vitro. Based on the published study and our preliminary results, we hypothesize that the epoxides lipids and/or inhibition of sEH may activate critical signaling pathways (such as PPAR? and PPAR?) to promote brown adipogenesis and that in vivo administering 19, 20-EDP, a prominent n-3 epoxide, or 19, 20-EDP combined with sEH inhibitor t-TUCB may promote functional brown adipogenesis and thermogenesis and increase energy expenditure, which in turn improve metabolic dysfunction in diet-induced obesity in mice. In light of the emerging role of BAT activation in human obesity treatment and prevention, it is critically important to identify novel endogenous pathways leading to brown adipogenesis, to understand the molecular mechanisms by which epoxide lipids promote brown adipogenesis, and to assess whether strategies to increase and/or stabilize epoxide lipids via sEH inhibition would be effective in increasing BAT mass and thermogenesis and improving metabolic dysfunction in commonly used preclinical models of obesity. To test our hypothesis, we propose the following specific aims: Aim 1: Dissect the pathways in brown preadipocytes that drive fatty acid epoxides production and promote cellular brown adipogenesis. Aim 2: Demonstrate the efficacy of 19, 20-EDP, t-TUCB, or a combination of EDP and t-TUCB to prevent and treat diet-induced obesity in mice by promoting brown adipogenesis and thermogenesis. The outcomes of this proposed project are (1) significant advancement of the understanding of BAT biology, leading to novel strategies to boost brown adipogenesis for obesity prevention and treatment; (2) extensive exposure and training of both undergraduate and graduate students to biomedical research in the areas of adipocyte biology and obesity, which is one of the major health crisis facing the nation today.